The present invention relates to the construction of flashlights and, more particularly, to a mechanism for allowing adjustment of the beam width provided by the flashlight.
U.S. Pat. Nos. 4,658,336 and 4,577,263 both describe a flashlight having a beam which adjusts by twisting a face cap at the forward end of the flashlight. Although generally functional, the design of the flashlights suffers from certain disadvantages. The receptacle holding the light bulb at the front of the flashlight is not removable, requiring that a separate end cap be provided for replacing batteries. Such a design is more expensive to fabricate and requires an additional seal in immersible units. Additionally, the receptacle holding the light bulb in the flashlight is not replaceable, complicating the repair should the focusing beam mechanism be damaged. Also, in the event of failure, the fragile light bulb must be separately replaced as it is part of no larger replacement unit. Finally, if the face cap is removed from the flashlight, the light bulb is exposed and subject to breakage.
Tekna, Redwood City, CA, sells a product line of miniature flashlight identified as the Tekna Lite.TM. 2, Micro-Lite.TM., and Mono-Lith.TM., which consists of a flashlight casing, a beam assembly, and a lens cowling which attaches to the forward end of the casing, urging the beam assembly against the batteries therein. The flashlight operates by urging the beam assembly rearward against a pair of fixed conductors axially aligned within the casing. When a conductive ring on the back of the beam assembly is brought into contact with the conductors, the light bulb in the beam assembly is energized. The parabolic reflector and light bulb within the beam assembly, however, are positionally fixed relative to one another, and no provision is made for beam width adjustment.
It would be desirable to provide a flashlight construction having a focusing beam mechanism, where the focusing beam mechanism can be completely removed from the forward end of the flashlight casing to allow for battery replacement. Such a construction eliminates the need for a detachable rear cap, reducing the number of seals required to provide an immersible unit. It would be further desirable that the focusing beam assembly be provided in a self-contained unit which would allow for replacement of the unit should a failure occur in the focusing beam mechanism. Such a construction would also eliminate the need for separately replacing fragile flashlight bulbs and would greatly limit the exposure of such bulbs to breakage when the flashlight unit is partially disassembled. Such a self-contained focusing beam assembly would also allow replacement of fixed beam assemblies in previously constructed flashlights when it is desired to add a focusing beam capability. It would further allow the user the option of selecting a fixed beam assembly or a focusing beam assembly as desired.